As the number of older people increases, the number of cataract patients has increased. It is common practice that cornea endothelium cells are checked before and after a cornea operation. The conventional check uses specular photography (photography of cornea endothelium cells by reflected rays of light that has been projected on the cornea), in which the following methods are used to obtain decision reference data:
1. Grid method--with a grid superimposed on a magnified photograph of cornea endothelium, the number of cells in the grid of specified intervals is counted and converted into the number of cells per mm.sup.2 (cell density);
2. Cell sizer method--a model whose cell density and coefficient of variation (CV) are known is previously prepared, and the cell density and the CV are determined by comparing it with the cornea endothelium photograph;
3. Digitizer method--coordinates of vertices of a cell (e.g. coordinates of points 1, 2, 3, 4, 5, and 6, which are vertices of the profile of a hexagonal cell as shown in FIG. 1) are entered into a computer, and the correct morphology of the individual cells is determined by the following equations:
Equation 1 EQU Cell area: Ar=1/2.SIGMA.((X.sub.n .times.Y.sub.n+1)-(X.sub.n+2 .times.Y.sub.n)) (.mu.m.sup.2) ##EQU1##
Equation 3 EQU Cell density: CD=1000000/Ave (pcs/M.sup.2) ##EQU2##
Equation 5 EQU Coefficient of variation: CV=SD/Ave
Equation 6
Hexagonal cell frequency: EQU Ap.sub.6 =(number of hexagonal cells)/N; and
4. Opposite-side input method--using the midpoints a.sub.c, b.sub.c, C.sub.c, and d.sub.c of opposite two sides of mutually adjoining cells A, B, D, and D (as illustrated in FIG. 2), the cell area is approximated by determining the area of an equilateral hexagon circumscribing a circle whose diameter is formed by each pair of midpoints. In this case, for example, the area of the cell A is as follows: ##EQU3##
The above-described conventional methods have the following problems:
1. The grid method allows only the determination of cell density;
2. The cell sizer method, although allowing determination of cell density and coefficient of variation, results in variations among persons who perform the comparison and therefore, may generate incorrect values;
3. The digitizer method, although obtaining all morphological data needed for clinical treatment necessitates a great deal of input labor, which is unsuitable for practical use; and
4. The opposite-side input method, although requiring less input, does not generate the polygonal number (hexagonal cell frequency, which is a decision criterion for doctors).
The present invention has been developed in view of the above-mentioned problems. An object of the present invention is therefore to provide a method for computing morphology of cornea endothelium cells, which solves the various disadvantages of the conventionally practiced methods and which allows profiles of cells to be reproduced simply by entering center points of the cells of a two-dimensional continuous cell image, so that all morphological data needed for clinical treatment equivalent to the digitizer method can be obtained with input labor far less than in the digitizer method.
To achieve the above object, the present invention provides a method for computing morphology of cornea endothelium cells, comprising the steps of:
(a) determining peripheral points within a specified distance from a center point of a selected one of the plurality of cells;
(b) sorting the peripheral points in a predetermined direction;
(c) determining an angle formed by first and second successive peripheral points in the predetermined direction and the center point;
(d) determining a first distance between the first successive peripheral point and a third successive peripheral point in the predetermined direction and a second distance between the center point and the second successive peripheral point;
(e) excluding one of the first and second successive peripheral points which is further from the center point, if the angle is less than a specified angle;
(f) excluding the second successive peripheral point if the first distance is less than the second distance;
(g) repeating steps (a)-(f) for remaining cells surrounding the selected one of the plurality of cells;
(h) determining an average distance between remaining peripheral points and the center point;
(i) determining a first point on a first line, connecting the center point and a first remaining peripheral point, by proportionally dividing a distance between the center point and the first remaining peripheral point according to the average distance between the remaining peripheral points and the center point and determining a first perpendicular line, perpendicular to the first line at the first point;
(j) determining a second point on a second line, connecting the center point and a second remaining peripheral point by proportionally dividing a distance between the center point and the second remaining peripheral point according to the average distance between the remaining peripheral points and the center point and determining a second perpendicular line, perpendicular to the second line at the second point;
(k) determining a first vertex of the selected one of the plurality of cells at an intersection of the first perpendicular line and the second perpendicular line;
(l) repeating steps (i)-(k) for each remaining peripheral point to determine all vertices of the selected one of the plurality of cells; and
(m) determining the morphology of the plurality of cells from coordinates of all vertices of the selected one of the plurality of cells.
To further achieve the above object, the specified distance is of 2.5 to 3.5 times a distance from the center point to a closest peripheral point.
To further achieve the above object, the specified angle is 20 to 40 degrees.
To further achieve the above object, if the angle formed by the first and second peripheral points in the predetermined direction and the center point is greater than 90 to 110 degrees, the center point is a center point of a peripheral cell.
To further achieve the above object, when an angle formed by the first successive peripheral point, the center point, and the third successive peripheral point is greater than 120 to 140 degrees, the second peripheral point is retained.
To further achieve the above object, the first and second points are determined by proportionally dividing according to a square to a fourth power of the average distances.
To further achieve the above object, the plurality of cells are cornea endothelium cells.
To further achieve the above object, the predetermined direction is clockwise or counter-clockwise.